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The geometry of a closed form

Marisa Fernández, Raúl Ibáñez, Manuel de León (1998)

Banach Center Publications

It is proved that a closed r-form ω on a manifold M defines a cohomology (called ω-coeffective) on M. A general algebraic machinery is developed to extract some topological information contained in the ω-coeffective cohomology. The cases of 1-forms, symplectic forms, fundamental 2-forms on almost contact manifolds, fundamental 3-forms on G 2 -manifolds and fundamental 4-forms in quaternionic manifolds are discussed.

The Gleason-Kahane-Zelazko theorem and function algebras

Edoardo Vesentini (2005)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

A theorem due to A. Gleason, J.-P. Kahane and W. Zelazko characterizes continuous characters within the space of all continuous linear forms of a locally multiplicatively convex, sequentially complete algebra. The present paper applies these results to investigate linear isometries of Banach algebras (with particular attention to normal uniform algebras) and of some locally multiplicatively convex algebras. The locally multiplicatively convex algebra of all holomorphic functions on a domain, will...

The Gleason-Kahane-Żelazko theorem and its generalizations

A. Sourour (1994)

Banach Center Publications

This expository article deals with results surrounding the following question: Which pairs of Banach algebras A and B have the property that every unital invertibility preserving linear map from A to B is a Jordan homomorphism?

The group of automorphisms of L is algebraically reflexive

Félix Cabello Sánchez (2004)

Studia Mathematica

We study the reflexivity of the automorphism (and the isometry) group of the Banach algebras L ( μ ) for various measures μ. We prove that if μ is a non-atomic σ-finite measure, then the automorphism group (or the isometry group) of L ( μ ) is [algebraically] reflexive if and only if L ( μ ) is *-isomorphic to L [ 0 , 1 ] . For purely atomic measures, we show that the group of automorphisms (or isometries) of ( Γ ) is reflexive if and only if Γ has non-measurable cardinal. So, for most “practical” purposes, the automorphism group...

The Gruenhage property, property *, fragmentability, and σ-isolated networks in generalized ordered spaces

Harold Bennett, David Lutzer (2013)

Fundamenta Mathematicae

We examine the Gruenhage property, property * (introduced by Orihuela, Smith, and Troyanski), fragmentability, and the existence of σ-isolated networks in the context of linearly ordered topological spaces (LOTS), generalized ordered spaces (GO-spaces), and monotonically normal spaces. We show that any monotonically normal space with property * or with a σ-isolated network must be hereditarily paracompact, so that property * and the Gruenhage property are equivalent in monotonically normal spaces....

Currently displaying 341 – 360 of 1071